This game is a favourite, so I keep making it because I know how motivating it is for intervention. It's the repetition that corrects the skill deficit so I know it will work.
I developed this game with matching pictures because the spelling of the 'er' sound can be a problem for some students for years before I get to see them. This is when games work well. You just have to make sure that the game is sufficiently motivating (fun) and targets the skill deficit directly. Then make sure that the game is played regularly. I even send games home for Family Fun Time when I know parents are keen to be involved. This is the quickest way to see progress. Adding it to a Literacy Centre would also work.
This game is included in my Bossy R Bundle with five Posters if you wish to address a wider range of skills and interest levels.